API_STRINGS.md

Strings Package Equivalents

Replace common strings package functions with fmt equivalents:

Go Standard	fmt Equivalent
strings.Builder	c:= Convert() c.Write(a) c.Write(b) c.String()
strings.Contains()	Contains(s, substr)
strings.Index()	Index(s, substr)
strings.LastIndex()	LastIndex(s, substr)
strings.Join()	Convert(slice).Join(sep).String() or JoinSlice(elems, sep)
strings.Repeat()	Convert(s).Repeat(n).String() or Repeat(s, n)
strings.Replace()	Convert(s).Replace(old, new, n).String()
strings.ReplaceAll()	ReplaceAll(s, old, new)
strings.Split()	Split(s, separator...)
strings.ToLower()	Convert(s).ToLower().String() or ToLower(s)
strings.ToUpper()	Convert(s).ToUpper().String() or ToUpper(s)
strings.TrimSpace()	Convert(s).TrimSpace().String() or TrimSpace(s)
strings.TrimPrefix()	Convert(s).TrimPrefix(prefix).String() or TrimPrefix(s, prefix)
strings.TrimSuffix()	Convert(s).TrimSuffix(suffix).String() or TrimSuffix(s, suffix)
strings.HasPrefix()	HasPrefix(s, prefix)
strings.HasSuffix()	HasSuffix(s, suffix)
(Utility)	Matches(s, terms...)

Drop-in stdlib-signature wrappers (strings.go)

Contains, Index, LastIndex, HasPrefix, HasSuffix, Split already match the stdlib strings signature and are used directly.

For the chain-only operations (TrimSpace, TrimPrefix, TrimSuffix, ToLower, ToUpper, Repeat, Replace, Join), strings.go adds thin package-level functions with the exact stdlib signature, implemented on top of the Convert(...) chain. This avoids the most common migration mistake — calling a chain method as if it were a package function (or vice versa) without knowing the full chain API:

Go Standard	fmt Equivalent
strings.TrimSpace(s)	TrimSpace(s)
strings.TrimPrefix(s, prefix)	TrimPrefix(s, prefix)
strings.TrimSuffix(s, suffix)	TrimSuffix(s, suffix)
strings.ToLower(s)	ToLower(s)
strings.ToUpper(s)	ToUpper(s)
strings.Repeat(s, count)	Repeat(s, count)
strings.ReplaceAll(s, old, new)	ReplaceAll(s, old, new)
strings.Join(elems, sep)	JoinSlice(elems, sep)

JoinSlice is named differently from Join because that name is already taken by Conv.Join (a chain method that takes the slice as the receiver).

Other String Transformations

Convert("hello world").CamelUp().String()  // out: "HelloWorld"
Convert("hello world").SnakeLow().String() // out: "hello_world"

String Search & Operations

// Search and count
pos := Index("hello world", "world")                  // out: 6 (first occurrence)
found := Contains("hello world", "world")              // out: true
count := Count("abracadabra", "abra")       // out: 2

// Prefix / Suffix checks
isPref := HasPrefix("hello", "he")          // out: true
isSuf := HasSuffix("file.txt", ".txt")      // out: true

// Note: this library follows the standard library semantics for prefixes/suffixes:
// an empty prefix or suffix is considered a match (HasPrefix(s, "") == true,
// HasSuffix(s, "") == true).

// Find last occurrence (useful for file extensions)
pos := LastIndex("image.backup.jpg", ".")             // out: 12
if pos >= 0 {
    extension := "image.backup.jpg"[pos+1:]           // out: "jpg"
}

// Multi-term searching (AND semantics, with internal ToLower() normalization)
foundAll := Matches("Hello World", "hello", "world")   // out: true
noMatch  := Matches("Hello World", "hello", "xyz")     // out: false

// ⚠️ Note: Index, Contains, LastIndex and Matches are global functions, not methods.
// Do NOT use: Convert(s).Contains(substr) // ❌ Incorrect, will not compile
// Use:        Index(s, substr)            // ✅ Correct
//             Contains(s, substr)         // ✅ Correct
//             LastIndex(s, substr)        // ✅ Correct
//             Matches(s, terms...)        // ✅ Correct

// Replace operations
Convert("hello world").Replace("world", "Go").String() // out: "hello Go"
Convert("test 123 test").Replace(123, 456).String()    // out: "test 456 test"

String Splitting & Joining

// Split strings (always use Convert(...).Split(...))
parts := Convert("apple,banana,cherry").Split(",")
// out: []string{"apple", "banana", "cherry"}

parts := Convert("hello world new").Split()  // Handles whitespace
// out: []string{"hello", "world", "new"}

// Join slices
Convert([]string{"Hello", "World"}).Join().String()    // out: "Hello World"
Convert([]string{"a", "b", "c"}).Join("-").String()    // out: "a-b-c"

String Trimming & Cleaning

// TrimSpace operations
Convert("  hello  ").TrimSpace().String()                    // out: "hello"
Convert("prefix-data").TrimPrefix("prefix-").String()   // out: "data"
Convert("file.txt").TrimSuffix(".txt").String()         // out: "file"

// Repeat strings
Convert("Go").Repeat(3).String()                        // out: "GoGoGo"