graph.go

@@ -127,31 +127,23 @@ func renderEdges(n node) []renderEdge {
 		return es
 	case *template:
 		var es []renderEdge
-		add := func(name, operand string) {
-			a := splitArm(name, n.refs)
+		add := func(a arm, operand string) {
 			c := n.head(a.key)
 			if c == nil {
 				return
 			}
 			for _, leaf := range pathLeaves(c, a.tail) {
-				es = append(es, renderEdge{leaf, name, operand})
+				es = append(es, renderEdge{leaf, a.name, operand})
 			}
 		}
-		_ = eachToken(n.format, func(t ftoken) error {
-			if t.kind != 'b' {
-				return nil
+		for _, o := range n.ops {
+			for _, a := range o.operands {
+				add(a, o.fn)
 			}
-			if fn, _, isFunc := funcCall(t.body); isFunc {
-				for _, operand := range tokenOperands(t.body) {
-					add(operand, fn)
-				}
-				return nil
+			for _, a := range o.arms {
+				add(a, "")
 			}
-			for _, name := range splitOutside(t.body, '|') {
-				add(name, "")
-			}
-			return nil
-		})
+		}
 		return es
 	case *table:
 		return []renderEdge{{to: n.format, label: "format"}}

holdfence.go

@@ -15,7 +15,7 @@ func heldCheck(path string, n node) error {
 	if !ok || len(t.held) == 0 {
 		return nil
 	}
-	readers := boundReaders(t.format, t.bound, t.refs)
+	readers := boundReaders(t.ops, t.bound)
 	for _, head := range heldHeads(t) {
 		if _, isPath := t.bound[head]; isPath && isRef(head) {
 			continue
@@ -87,21 +87,14 @@ func checkHeadHeld(t *template, head string, readers []reader) error {
 
 // operandReader names the builtin whose operand holds head.
 func operandReader(t *template, head string) string {
-	fn := ""
-	_ = eachToken(t.format, func(tok ftoken) error {
-		if tok.kind != 'b' || fn != "" {
-			return nil
-		}
-		if name, _, isFunc := funcCall(tok.body); isFunc {
-			for _, operand := range tokenOperands(tok.body) {
-				if splitArm(operand, t.refs).key == head {
-					fn = name
-				}
+	for _, o := range t.ops {
+		for _, a := range o.operands {
+			if a.key == head {
+				return o.fn
 			}
 		}
-		return nil
-	})
-	return fn
+	}
+	return ""
 }
 
 // coverPath collects what holding one path pins: every choice level the path
@@ -183,8 +176,8 @@ func renders(n node, want, seen map[node]bool) bool {
 // disagree. Reads are compared in sorted order, so which pair is reported does not
 // depend on where the tokens sit.
 // docs/decisions.md#a-bare-reference-draws-each-time-a-reference-path-is-held
-func checkNoOverlap(format string, bound map[string]string, refs map[string]refBinding) error {
-	names := boundReaders(format, bound, refs)
+func checkNoOverlap(ops []op, bound map[string]string) error {
+	names := boundReaders(ops, bound)
 	// Stable over one format-order scan, so two readers of one name (a token and a
 	// calc operand both naming "p") are reported as the format writes them.
 	sort.SliceStable(names, func(i, j int) bool { return names[i].path < names[j].path })
@@ -205,28 +198,20 @@ type reader struct{ name, path, label string }
 // boundReaders lists every way a format reaches a bound sibling field, in the order the
 // format writes them. An operand renders its field, so it names a level exactly
 // as a token does; one scan finds both, which is what puts them in one order.
-func boundReaders(format string, bound map[string]string, refs map[string]refBinding) []reader {
+func boundReaders(ops []op, bound map[string]string) []reader {
 	var names []reader
-	_ = eachToken(format, func(t ftoken) error {
-		if t.kind != 'b' {
-			return nil
-		}
-		if fn, _, isFunc := funcCall(t.body); isFunc {
-			for _, operand := range tokenOperands(t.body) {
-				a := splitArm(operand, refs)
-				if _, isBound := bound[a.key]; isBound && !isRef(a.key) {
-					names = append(names, reader{a.name, a.path, fmt.Sprintf("%s operand %q", fn, operand)})
-				}
+	for _, o := range ops {
+		for _, a := range o.operands {
+			if _, isBound := bound[a.key]; isBound && !isRef(a.key) {
+				names = append(names, reader{a.name, a.path, fmt.Sprintf("%s operand %q", o.fn, a.name)})
 			}
-			return nil
 		}
-		for _, a := range splitArms(t.body, refs) {
+		for _, a := range o.arms {
 			if _, isBound := bound[a.key]; isBound && !isRef(a.key) {
 				names = append(names, reader{a.name, a.path, "token {" + a.name + "}"})
 			}
 		}
-		return nil
-	})
+	}
 	return names
 }
 
@@ -234,16 +219,10 @@ func boundReaders(format string, bound map[string]string, refs map[string]refBin
 // {uppercase(w)} would read one draw twice, where {w} {w} alone draws twice. The
 // error names the single-token spelling.
 // docs/decisions.md#a-bare-reference-draws-each-time-a-reference-path-is-held
-func checkNoRepeatedRead(format string, c formatOps, refs map[string]refBinding) error {
+func checkNoRepeatedRead(c formatOps) error {
 	count := map[string]int{}
-	return eachToken(format, func(t ftoken) error {
-		if t.kind != 'b' {
-			return nil
-		}
-		if _, _, isFunc := funcCall(t.body); isFunc {
-			return nil
-		}
-		for _, a := range splitArms(t.body, refs) {
+	for _, o := range c.ops {
+		for _, a := range o.arms {
 			if len(a.tail) > 0 || !c.held[a.key] {
 				continue
 			}
@@ -251,6 +230,6 @@ func checkNoRepeatedRead(format string, c formatOps, refs map[string]refBinding)
 				return fmt.Errorf("token {%s} is repeated, and %s holds %q to one draw per expansion; write {%s} once", a.name, c.holder[a.key], a.key, a.name)
 			}
 		}
-		return nil
-	})
+	}
+	return nil
 }

inline.go

@@ -107,8 +107,15 @@ func loneReference(arg string) (string, bool) {
 		raw = m["format"]
 	}
 	format, isString := raw.(string)
-	body, lone := loneRef(format)
-	if !isString || !lone {
+	if !isString {
+		return "", false
+	}
+	toks, err := parseFormat(format)
+	if err != nil {
+		return "", false
+	}
+	body, lone := loneRef(toks)
+	if !lone {
 		return "", false
 	}
 	if strings.HasPrefix(body, "/") {
@@ -161,7 +168,7 @@ func linkNodeRefs(scope nodeScope, root map[string]node) error {
 			return nil
 		}
 		t.keyDrawGroup("")
-		for _, name := range refTokens(t.format) {
+		for _, name := range refTokens(t.tokens) {
 			sigil, rest, err := refShape(name)
 			if err != nil {
 				return fmt.Errorf("%s: reference {%s}: %w", path, name, err)

node.go

@@ -45,6 +45,7 @@ func (*null) isNode() {}
 type template struct {
 	// Filled by `compileString`, `compileTemplate` and `table.compileWhole`:
 	format     string
+	tokens     []formatToken
 	fields     map[string]node
 	repeat     int
 	separator  string
@@ -203,10 +204,14 @@ func jsonKind(v any) string {
 }
 
 func compileString(s string) (node, error) {
-	if err := checkTokens(s, nil); err != nil {
+	toks, err := parseFormat(s)
+	if err != nil {
 		return nil, err
 	}
-	t := &template{format: s, repeat: 1, fromString: true}
+	if err := checkTokens(toks, nil); err != nil {
+		return nil, err
+	}
+	t := &template{format: s, tokens: toks, repeat: 1, fromString: true}
 	if err := t.compileRefFree(); err != nil {
 		return nil, err
 	}
@@ -214,7 +219,7 @@ func compileString(s string) (node, error) {
 }
 
 func (t *template) compileRefFree() error {
-	if len(refTokens(t.format)) > 0 {
+	if len(refTokens(t.tokens)) > 0 {
 		return nil
 	}
 	return t.compileFormat()
@@ -223,7 +228,7 @@ func (t *template) compileRefFree() error {
 // compileFormat compiles the format into ops, and applies the fences that need the
 // compiled reads.
 func (t *template) compileFormat() error {
-	c := compileOps(t.format, t.refs)
+	c := compileOps(t.tokens, t.refs)
 	t.ops, t.grow, t.bound, t.held, t.heldLocal = c.ops, c.grow, c.bound, c.held, c.heldLocal
 	t.fixed = true
 	for _, o := range t.ops {
@@ -234,10 +239,10 @@ func (t *template) compileFormat() error {
 	if t.fixed && len(t.ops) == 1 {
 		t.lit = t.ops[0].lit
 	}
-	if err := checkNoOverlap(t.format, t.bound, t.refs); err != nil {
+	if err := checkNoOverlap(t.ops, t.bound); err != nil {
 		return err
 	}
-	return checkNoRepeatedRead(t.format, c, t.refs)
+	return checkNoRepeatedRead(c)
 }
 
 func compileChoice(items []any, pos position) (node, error) {
@@ -331,13 +336,17 @@ func compileTemplate(m map[string]any, pos position) (node, error) {
 	if len(fields) == 0 && o.repeat == 1 && !o.weighted && o.datatype == DataTypeString && o.group == "" {
 		return nil, fmt.Errorf("an object holding only a format is a string; write %q", o.format)
 	}
-	if err := checkTokens(o.format, fields); err != nil {
+	toks, err := parseFormat(o.format)
+	if err != nil {
+		return nil, err
+	}
+	if err := checkTokens(toks, fields); err != nil {
 		return nil, err
 	}
 	if err := checkNestedDrawGroup(fields, o.group); err != nil {
 		return nil, err
 	}
-	t := &template{format: o.format, fields: fields, repeat: o.repeat, separator: o.separator, datatype: o.datatype, drawGroup: o.group, record: fieldPos == inColumn}
+	t := &template{format: o.format, tokens: toks, fields: fields, repeat: o.repeat, separator: o.separator, datatype: o.datatype, drawGroup: o.group, record: fieldPos == inColumn}
 	if err := t.compileRefFree(); err != nil {
 		return nil, err
 	}

reference.go

@@ -87,7 +87,7 @@ func linkRefs(root map[string]node) error {
 // category it sits in.
 // docs/decisions.md#a-category-never-references-itself-and-a-records-fences-run-at-load
 func linkTemplateRefs(folder []string, path, category string, t *template, root map[string]node) error {
-	names := refTokens(t.format)
+	names := refTokens(t.tokens)
 	if len(names) == 0 {
 		return nil
 	}
@@ -130,7 +130,7 @@ type columnRead struct {
 }
 
 func columnReadOf(t *template) *columnRead {
-	name, lone := loneRef(t.format)
+	name, lone := loneRef(t.tokens)
 	if !lone || t.repeat != 1 {
 		return nil
 	}
@@ -143,17 +143,11 @@ func columnReadOf(t *template) *columnRead {
 }
 
 // loneRef is the reference a format of one reference token and nothing else reads.
-func loneRef(format string) (string, bool) {
-	units, body := 0, ""
-	err := eachToken(format, func(t ftoken) error {
-		units++
-		body = t.body
-		return nil
-	})
-	if err != nil || units != 1 || !isRef(body) || strings.ContainsAny(body, "|(") {
+func loneRef(toks []formatToken) (string, bool) {
+	if len(toks) != 1 || toks[0].kind != 'f' || len(toks[0].names) != 1 || !isRef(toks[0].names[0]) {
 		return "", false
 	}
-	return body, true
+	return toks[0].names[0], true
 }
 
 // eachTemplate calls fn once per template, with the folder its category sits in
@@ -220,13 +214,15 @@ func resolveCategory(root map[string]node, segments []string) (head []string, ta
 }
 
 // refTokens returns the reference names a format reads, as tokens or as operands.
-func refTokens(format string) []string {
+func refTokens(toks []formatToken) []string {
 	var refs []string
 	seen := map[string]bool{}
-	for _, name := range append(fieldTokens(format), operandTokens(format)...) {
-		if isRef(name) && !seen[name] {
-			seen[name] = true
-			refs = append(refs, name)
+	for _, tok := range toks {
+		for _, name := range tok.names {
+			if isRef(name) && !seen[name] {
+				seen[name] = true
+				refs = append(refs, name)
+			}
 		}
 	}
 	return refs

table.go

@@ -324,16 +324,22 @@ func (t *table) checkCells() error {
 // compileWhole compiles the format a row renders whole through, over the columns
 // as its fields.
 func (t *table) compileWhole(format string) error {
-	for _, name := range fieldTokens(format) {
-		a := splitArm(name, nil)
-		if _, ok := t.col[a.key]; !ok && !isRef(a.key) && a.key != "" {
-			return fmt.Errorf("format names no column %q of %s; the columns are %v", a.key, t.file, t.columns)
-		}
-	}
-	if err := checkTokens(format, t.fields); err != nil {
+	toks, err := parseFormat(format)
+	if err != nil {
 		return err
 	}
-	t.format = &template{format: format, fields: t.fields, repeat: 1, record: true, table: t}
+	for _, tok := range toks {
+		for _, name := range tok.names {
+			a := splitArm(name, nil)
+			if _, ok := t.col[a.key]; tok.kind == 'f' && !ok && !isRef(a.key) && a.key != "" {
+				return fmt.Errorf("format names no column %q of %s; the columns are %v", a.key, t.file, t.columns)
+			}
+		}
+	}
+	if err := checkTokens(toks, t.fields); err != nil {
+		return err
+	}
+	t.format = &template{format: format, tokens: toks, fields: t.fields, repeat: 1, record: true, table: t}
 	t.whole = &row{t}
 	return t.format.compileRefFree()
 }

template.go

@@ -57,6 +57,52 @@ func eachToken(format string, fn func(ftoken) error) error {
 	return nil
 }
 
+// formatToken is one parsed unit of a format: a literal run, a field alternation or a
+// builtin call.
+type formatToken struct {
+	kind  byte     // 'l' literal run, 'f' field alternation, 'b' builtin call
+	lit   string   // kind 'l'
+	body  string   // the braces' content, as written
+	fn    string   // kind 'b'
+	args  []string // kind 'b'
+	names []string // kind 'f': the '|' arms; kind 'b': the operands its builtin reads
+}
+
+// parseFormat is the one reading of a format's tokens: a '(' outside a selector makes
+// a token a call.
+func parseFormat(format string) ([]formatToken, error) {
+	var toks []formatToken
+	var lit strings.Builder
+	flush := func() {
+		if lit.Len() > 0 {
+			toks = append(toks, formatToken{kind: 'l', lit: lit.String()})
+			lit.Reset()
+		}
+	}
+	err := eachToken(format, func(t ftoken) error {
+		if t.kind == 'l' {
+			lit.WriteRune(t.r)
+			return nil
+		}
+		flush()
+		if indexOutside(t.body, '(') < 0 {
+			toks = append(toks, formatToken{kind: 'f', body: t.body, names: splitOutside(t.body, '|')})
+			return nil
+		}
+		name, args, ok := funcCall(t.body)
+		if !ok {
+			return fmt.Errorf("malformed function token {%s}", t.body)
+		}
+		toks = append(toks, formatToken{kind: 'b', body: t.body, fn: name, args: args, names: builtinOperands(name, args)})
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+	flush()
+	return toks, nil
+}
+
 // builtin is a format-string function invoked as {name(args)}. It receives the
 // session (its rng, and the {seq()} counters), the output emitted so far in the
 // current expansion (for derivations such as a checksum over preceding digits), and
@@ -119,15 +165,11 @@ func plural(n int) string {
 	return "s"
 }
 
-// checkFunc validates a function token at compile time: well-formed, naming a
-// known builtin, with the arg count that builtin takes and args its check accepts.
-// fields is passed through for the builtins (calc, the transforms) that validate
-// against them.
-func checkFunc(body string, fields map[string]node) error {
-	name, args, ok := funcCall(body)
-	if !ok {
-		return fmt.Errorf("malformed function token {%s}", body)
-	}
+// checkFunc validates a call at compile time: naming a known builtin, with the arg
+// count that builtin takes and args its check accepts. fields is passed through for
+// the builtins (calc, the transforms) that validate against them.
+func checkFunc(tok formatToken, fields map[string]node) error {
+	body, name, args := tok.body, tok.fn, tok.args
 	b, known := builtins[name]
 	if !known {
 		return fmt.Errorf("token {%s}: unknown function %q", body, name)
@@ -143,34 +185,38 @@ func checkFunc(body string, fields map[string]node) error {
 	return nil
 }
 
-// checkTokens validates a format string the way expand scans it, so every
-// "{token}" is balanced and names an existing field (or a known function). This
-// makes a typo'd or dangling reference a New-time error, never a random
-// render-time one.
-func checkTokens(format string, fields map[string]node) error {
-	return eachToken(format, func(t ftoken) error {
-		if t.kind != 'b' {
-			return nil
+// checkTokens proves every parsed token names an existing field or a known function,
+// so a typo'd or dangling reference is a New-time error.
+func checkTokens(toks []formatToken, fields map[string]node) error {
+	for _, t := range toks {
+		if err := checkToken(t, fields); err != nil {
+			return err
 		}
-		if indexOutside(t.body, '(') >= 0 { // a function token, not a field
-			return checkFunc(t.body, fields)
-		}
-		names := splitOutside(t.body, '|')
-		for _, name := range names {
+	}
+	return nil
+}
+
+func checkToken(t formatToken, fields map[string]node) error {
+	switch t.kind {
+	case 'b':
+		return checkFunc(t, fields)
+	case 'f':
+		for _, name := range t.names {
 			if isRef(name) {
 				if _, _, err := refShape(name); err != nil {
 					return fmt.Errorf("token {%s}: %w", t.body, err)
 				}
 				continue // its target is checked at New (see linkRefs)
 			}
-			if err := checkArm(name, fields, len(names) == 1); err != nil {
+			if err := checkArm(name, fields, len(t.names) == 1); err != nil {
 				return fmt.Errorf("token {%s}: %w", t.body, err)
 			}
 		}
 		// Last, so an arm broken on its own terms is reported as that: a repeat is
 		// the consequence of such a mistake, not the mistake itself.
-		return checkNoRepeatedArm(t.body, names)
-	})
+		return checkNoRepeatedArm(t.body, t.names)
+	}
+	return nil
 }
 
 // checkArm validates one sibling name or path against a template's fields.
@@ -210,32 +256,16 @@ func hintableRef(name string) bool {
 	return checkPathNames(name) == nil
 }
 
-// tokenOperands lists the fields one {token} body reads as operands, empty for a
-// field token or a builtin that reads none.
-func tokenOperands(body string) []string {
-	name, args, ok := funcCall(body)
-	if !ok {
-		return nil
-	}
+// builtinOperands lists the fields a call reads as operands, empty for a builtin that
+// reads none, or a call checkFunc refuses.
+func builtinOperands(name string, args []string) []string {
 	b, known := builtins[name]
-	if !known || b.operands == nil {
+	if !known || b.operands == nil || (b.arity >= 0 && len(args) != b.arity) {
 		return nil
 	}
 	return b.operands(args)
 }
 
-// operandTokens lists every operand the builtins in a format read.
-func operandTokens(format string) []string {
-	var names []string
-	_ = eachToken(format, func(t ftoken) error {
-		if t.kind == 'b' {
-			names = append(names, tokenOperands(t.body)...)
-		}
-		return nil
-	})
-	return names
-}
-
 // checkNoRepeatedArm rejects {a|a|b}: an alternation picks its arms evenly, so a
 // repeated one is a second spelling of weight. The error names the spelling that
 // does skew a pick.
@@ -253,20 +283,6 @@ func checkNoRepeatedArm(body string, names []string) error {
 	return nil
 }
 
-// fieldTokens returns the field and reference names a format renders via {name}
-// or {a|..b} tokens (function tokens, which carry no field edges, are excluded).
-// These are exactly the child nodes expand recurses into, through readField.
-func fieldTokens(format string) []string {
-	var names []string
-	_ = eachToken(format, func(t ftoken) error {
-		if t.kind == 'b' && indexOutside(t.body, '(') < 0 {
-			names = append(names, splitOutside(t.body, '|')...)
-		}
-		return nil
-	})
-	return names
-}
-
 // arm is one alternative of a {a|b} token or one operand, split into the key
 // `template.head` resolves and the tail of a dotted path into it. A non-empty tail
 // is what makes the arm a bound draw: its head is drawn once per expansion (see
@@ -308,16 +324,6 @@ func pathArm(name, key string, segs []string) arm {
 	return arm{name: name, key: key, tail: segs, levels: levels, path: key + "." + strings.Join(segs, ".")}
 }
 
-// splitArms splits a token body's '|' alternatives.
-func splitArms(body string, refs map[string]refBinding) []arm {
-	parts := splitOutside(body, '|')
-	arms := make([]arm, len(parts))
-	for i, p := range parts {
-		arms[i] = splitArm(p, refs)
-	}
-	return arms
-}
-
 // checkSegments rejects an unfinished path: "{a.}" and "{a..b}" each have a
 // segment naming nothing. A field really named "" would otherwise make them
 // resolve, so a typo would read as a path that worked.
@@ -345,9 +351,8 @@ type callFn func(s *session, emitted string, operands []string) string
 // or a builtin already bound to its args. compile builds these so render never
 // re-scans the format.
 type op struct {
-	kind byte   // 'l' literal run, 'f' field alternation, 'b' builtin
-	lit  string // kind 'l'
-	arms []arm  // kind 'f': the '|' alternatives, split into key and path once
+	formatToken
+	arms []arm // kind 'f': the '|' alternatives, split into key and path once
 	call callFn
 	// operands are the fields the builtin reads, in the order its operands func
 	// fixed; expand reads them before the call. nil for a builtin that reads none.
@@ -391,53 +396,41 @@ func (c *formatOps) holdName(a arm, label string) {
 	}
 }
 
-func (c *formatOps) function(body string, refs map[string]refBinding) {
-	name, args, _ := funcCall(body)
+func (c *formatOps) function(tok formatToken, refs map[string]refBinding) {
 	var operands []arm
-	for _, operand := range tokenOperands(body) {
+	for _, operand := range tok.names {
 		a := splitArm(operand, refs)
-		c.holdName(a, fmt.Sprintf("%s operand %q", name, operand))
+		c.holdName(a, fmt.Sprintf("%s operand %q", tok.fn, operand))
 		operands = append(operands, a)
 	}
-	c.ops = append(c.ops, op{kind: 'b', call: builtins[name].prep(args), operands: operands})
+	c.ops = append(c.ops, op{formatToken: tok, call: builtins[tok.fn].prep(tok.args), operands: operands})
 }
 
-func (c *formatOps) field(body string, refs map[string]refBinding) {
-	arms := splitArms(body, refs)
-	for _, a := range arms {
-		if len(a.tail) > 0 {
-			c.holdName(a, "token {"+a.name+"}")
+func (c *formatOps) field(tok formatToken, refs map[string]refBinding) {
+	arms := make([]arm, len(tok.names))
+	for i, name := range tok.names {
+		arms[i] = splitArm(name, refs)
+		if len(arms[i].tail) > 0 {
+			c.holdName(arms[i], "token {"+arms[i].name+"}")
 		}
 	}
-	c.ops = append(c.ops, op{kind: 'f', arms: arms})
+	c.ops = append(c.ops, op{formatToken: tok, arms: arms})
 }
 
-// compileOps compiles a format string. Call checkTokens first: it is what proves
-// the scan and every token are valid.
-func compileOps(format string, refs map[string]refBinding) formatOps {
+// compileOps compiles a parsed format. Call checkTokens first: it is what proves
+// every token valid.
+func compileOps(toks []formatToken, refs map[string]refBinding) formatOps {
 	var c formatOps
-	var lit strings.Builder
-	flush := func() {
-		if lit.Len() > 0 {
-			c.grow += lit.Len()
-			c.ops = append(c.ops, op{kind: 'l', lit: lit.String()})
-			lit.Reset()
+	for _, tok := range toks {
+		switch tok.kind {
+		case 'l':
+			c.grow += len(tok.lit)
+			c.ops = append(c.ops, op{formatToken: tok})
+		case 'b':
+			c.function(tok, refs)
+		case 'f':
+			c.field(tok, refs)
 		}
 	}
-	_ = eachToken(format, func(t ftoken) error {
-		switch t.kind {
-		case 'l':
-			lit.WriteRune(t.r)
-		case 'b':
-			flush()
-			if _, _, isFunc := funcCall(t.body); isFunc {
-				c.function(t.body, refs)
-			} else {
-				c.field(t.body, refs)
-			}
-		}
-		return nil
-	})
-	flush()
 	return c
 }

todo.md

@@ -19,10 +19,6 @@ Self-sufficiency 5.6), every seat capped by Locality or Self-sufficiency.
 
 This round, in order:
 
-- Parse a format once and have the fences read `t.ops`: `eachToken` rescans the format
-  in `fieldTokens`, `operandTokens`, `boundReaders`, `renderEdges`, `loneRef`,
-  `operandReader`, `checkNoRepeatedRead` and `compileOps`, and function-versus-field is
-  decided by `indexOutside(body, '(')` in two of them and by `funcCall` in the rest.
 - Name `pathWalk`'s modes: render, probe, check and cover are chosen today by which
   callbacks are nil and whether `draws` is, and `walkChoice` returns `nil, nil` where
   none is set. Make the render mode reachable only through a proved path: a walk that

value.go

@@ -152,12 +152,12 @@ func (p *valueProof) template(t *template) proven {
 		v.notOperand = notOneValue(t.format, "{int()}, {float()}, {seq()}, {digits()} or {calc()}")
 		return v
 	}
-	body := t.format[1 : len(t.format)-1]
-	name, args, isFunc := funcCall(body)
+	o := t.ops[0]
+	body, name, args := o.body, o.fn, o.args
 	switch _, isTransform := transforms[name]; {
-	case !isFunc:
+	case o.kind == 'f':
 		var leaves []node
-		for _, a := range splitArms(body, t.refs) {
+		for _, a := range o.arms {
 			leaves = append(leaves, pathLeaves(t.head(a.key), a.tail)...)
 		}
 		return p.unite(leaves)