108 lines
3.0 KiB
Markdown
108 lines
3.0 KiB
Markdown
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## 11. Advanced Topics
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### 11.1 Dynamic Code Evaluation
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The `eval` operator executes code dynamically at runtime by parsing and executing a TokenString.
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**Syntax**: `{ code } eval`
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**Examples**:
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```
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// Evaluate simple expression
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"2 3 +" eval // Pushes 5
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// Build and execute code
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"(Multiplyable -- Multiplyable) { dup * } ::square fn" eval
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5 square // 25
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// Dynamic dispatch
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operation_name " get" concat eval
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```
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**Use Cases**:
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- Building code at runtime
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- Dynamic dispatch based on runtime values
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- Implementing interpreters or REPLs
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- Meta-programming
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**Warnings**:
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- Eval introduces runtime overhead (parsing)
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- Type safety is reduced (types checked at eval time, not compile time)
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- Security risk if evaluating untrusted code
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- Use sparingly and prefer static alternatives when possible
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### 11.2 Identifier Literals
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Identifier literals use the `::` prefix to push an identifier as a value rather than executing it.
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**Syntax**: `::name`
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**Context-Dependent Rules**:
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**In function bodies and eval**: `::` is required for identifier literals
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```
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::Point // Pushes identifier "Point"
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::Addable // Pushes identifier "Addable"
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```
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**In trait definitions**: `::` is not allowed (identifiers are method names)
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```
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{
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(Self -- ) draw: // "draw:" is a method name, not a literal
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} ::Drawable trait
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```
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**In trait implementations**: `::` is not allowed (identifiers are method names)
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```
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::Drawable {
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(Self -- ) { ... } draw: // "draw:" is a method name
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} ::Rectangle impl
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```
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**Use Cases**:
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- Defining structs: `(T T --) { x: y: } ::Point<T> struct`
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- Defining traits: `{ ... } ::Drawable trait`
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- Field access: `point ::x get`
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- Dynamic trait operations
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- Meta-programming
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### 11.3 Standard Library
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The standard library provides I/O, string operations, type conversions, and utility functions. All standard library functions are automatically in scope (no imports needed in current version).
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**I/O Operations**:
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```
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"Hello" print // Print string to stdout
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"Enter name: " input // Read line from stdin
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"file.txt" read // Read file contents as string
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"data" "file.txt" write // Write string to file
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```
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**String Operations**:
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```
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"hello" " world" concat // Concatenate strings
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"hello" length // Get string length
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"hello" 1 3 substr // Extract substring
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"a,b,c" "," split // Split by delimiter
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["a" "b"] "," join // Join with delimiter
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```
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**Type Conversion**:
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```
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42 to_f64 // Convert i32 to f64
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3.14 to_i32 // Convert f64 to i32 (truncates)
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"123" parse // Parse string to inferred type
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42 to_str // Convert to string
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```
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**Array Operations**:
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- Element access: `at`, `slice`
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- Information: `length`, `shape`
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- Combinators: `map`, `filter`, `reduce`, `each`
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- Manipulation: `concat`, `reverse`, `transpose`, `window`
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> **Complete Reference**: See Appendix A for the full standard library reference with all functions, signatures, and examples.
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---
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