feat(awk): implement phase 3 practical features

SHELL_FEATURES.md

@@ -7,7 +7,7 @@ The in-shell `help` command mirrors these feature categories: run `help` for a c
 
 ## Builtins
 
-- ✅ `awk [-F SEP] [-v NAME=VALUE] ['PROGRAM'|-f PROGRAM-FILE] [FILE]...` — pattern scanning and text processing; supports BEGIN/main/END rules, read-only fields (`$0`, `$1`, `$NF`), `NF`/`NR`/`FNR`/`FILENAME`, `FS`/`OFS`/`ORS`, `print`, `printf`, scalar assignment, arithmetic/comparison/boolean expressions, regex patterns and `~`/`!~`, string concatenation, `if`/`else`, `next`, and scalar builtins (`length`, `substr`, `index`, `tolower`, `toupper`, `int`); `system()`, command pipes, output redirection, `getline`, arrays, loops, regex `FS`, and field mutation are rejected or deferred
+- ✅ `awk [-F SEP] [-v NAME=VALUE] ['PROGRAM'|-f PROGRAM-FILE] [FILE]...` — pattern scanning and text processing; supports BEGIN/main/END rules, fields and field mutation (`$0`, `$1`, `$NF`), `NF`/`NR`/`FNR`/`FILENAME`, `FS`/`OFS`/`ORS`, regex `FS`, `print`, `printf`, scalar and associative array assignment, `split`, `in`, `delete`, `for`, `while`, `break`, `continue`, range patterns, arithmetic/comparison/boolean expressions, regex patterns and `~`/`!~`, string concatenation, `if`/`else`, `next`, `ENVIRON`, and scalar builtins (`length`, `substr`, `index`, `tolower`, `toupper`, `int`); `system()`, command pipes, output redirection, `getline`, user-defined functions, and many POSIX/GNU awk builtins remain rejected or deferred
 - ✅ `break` — exit the innermost `for` loop
 - ✅ `cat [-AbeEnstTuv] [FILE]...` — concatenate files to stdout; supports line numbering, blank squeezing, and non-printing character display
 - ✅ `continue` — skip to the next iteration of the innermost `for` loop

analysis/symbols_builtins.go

@@ -636,7 +636,6 @@ var builtinAllowedSymbols = []string{
 	"slices.Reverse",                                      // 🟢 reverses a slice in-place; pure function, no I/O.
 	"slices.SortFunc",                                     // 🟢 sorts a slice with a comparison function; pure function, no I/O.
 	"slices.SortStableFunc",                               // 🟢 stable sort with a comparison function; pure function, no I/O.
-	"strings.Repeat",                                      // 🟢 returns a string of n repetitions; pure function, no I/O.
 	"strconv.Atoi",                                        // 🟢 string-to-int conversion; pure function, no I/O.
 	"strconv.ErrRange",                                    // 🟢 sentinel error value for overflow; pure constant.
 	"strconv.FormatBool",                                  // 🟢 bool-to-string conversion; pure function, no I/O.
@@ -661,6 +660,7 @@ var builtinAllowedSymbols = []string{
 	"strings.Join",                                        // 🟢 concatenates a slice of strings with a separator; pure function, no I/O.
 	"strings.NewReader",                                   // 🟢 wraps a string as an io.Reader; pure in-memory, no I/O.
 	"strings.ReplaceAll",                                  // 🟢 replaces all occurrences of a substring; pure function, no I/O.
+	"strings.Repeat",                                      // 🟢 returns a string of n repetitions; pure function, no I/O.
 	"strings.Split",                                       // 🟢 splits a string by separator into a slice; pure function, no I/O.
 	"strings.ToLower",                                     // 🟢 converts string to lowercase; pure function, no I/O.
 	"strings.ToUpper",                                     // 🟢 converts string to uppercase; pure function, no I/O.

builtins/awk/ast.go

@@ -47,10 +47,50 @@ type ifStmt struct {
 
 func (*ifStmt) stmtNode() {}
 
+type forInStmt struct {
+	varName   string
+	arrayName string
+	body      []stmt
+}
+
+func (*forInStmt) stmtNode() {}
+
+type forStmt struct {
+	init expr
+	cond expr
+	post expr
+	body []stmt
+}
+
+func (*forStmt) stmtNode() {}
+
+type whileStmt struct {
+	cond expr
+	body []stmt
+}
+
+func (*whileStmt) stmtNode() {}
+
 type nextStmt struct{}
 
 func (*nextStmt) stmtNode() {}
 
+type breakStmt struct{}
+
+func (*breakStmt) stmtNode() {}
+
+type continueStmt struct{}
+
+func (*continueStmt) stmtNode() {}
+
+type deleteStmt struct {
+	name  string
+	index expr
+	all   bool
+}
+
+func (*deleteStmt) stmtNode() {}
+
 type exprStmt struct {
 	x expr
 }
@@ -86,6 +126,13 @@ type varExpr struct {
 
 func (*varExpr) exprNode() {}
 
+type arrayRefExpr struct {
+	name  string
+	index expr
+}
+
+func (*arrayRefExpr) exprNode() {}
+
 type fieldExpr struct {
 	index expr
 }
@@ -113,6 +160,13 @@ type binaryExpr struct {
 
 func (*binaryExpr) exprNode() {}
 
+type rangeExpr struct {
+	start expr
+	end   expr
+}
+
+func (*rangeExpr) exprNode() {}
+
 type assignExpr struct {
 	op    string
 	left  expr

builtins/awk/awk.go

@@ -12,16 +12,17 @@
 //	awk [OPTION]... -f program-file [FILE]...
 //
 // This implements a practical, intentionally restricted awk profile: program
-// loading from an inline argument or -f files, -F one-character field
+// loading from an inline argument or -f files, -F field
 // separators, -v scalar variables, BEGIN/main/END rules, print and printf,
-// scalar assignment, if/else, next, arithmetic/comparison/boolean expressions,
-// regex patterns and match operators, string concatenation, scalar built-in
-// functions, and read-only fields/built-in variables such as $0, $1, NF, NR,
-// FNR, FILENAME, FS, OFS, and ORS.
+// scalar and associative array assignment, if/else, for/while loops, next,
+// arithmetic/comparison/boolean expressions, regex patterns and match
+// operators, regex field separators, string concatenation, scalar built-in
+// functions, split, delete, ENVIRON, and field/built-in variables such as $0,
+// $1, NF, NR, FNR, FILENAME, FS, OFS, and ORS.
 //
 // Blocked or deferred features include system(), command pipes, output
-// redirection, getline, arrays, loops, user-defined functions, regex FS, and
-// field mutation/$0 rebuilding.
+// redirection, getline, user-defined functions, and many additional POSIX/GNU
+// awk builtins.
 package awk
 
 import (
@@ -93,7 +94,7 @@ func registerFlags(fs *builtins.FlagSet) builtins.HandlerFunc {
 	help := fs.BoolP("help", "h", false, "print usage and exit")
 	var orderedOptions []orderedOption
 	fieldSep := fieldSeparatorOption{options: &orderedOptions}
-	fs.VarP(&fieldSep, "field-separator", "F", "use a single-character input field separator")
+	fs.VarP(&fieldSep, "field-separator", "F", "use an input field separator regular expression")
 	var programFiles stringList
 	fs.VarP(&programFiles, "file", "f", "read awk program from file")
 	assignments := assignmentOption{options: &orderedOptions}