Condition Operators

if

Syntax options:

if (bool) statement;
if (bool) statement; else statement;
if (bool) statement; elseif statement; else statement;

Example:

> if (1==0) "1==0\n".echo();  else "none\n".echo();
none

> if (1==0) "1==0\n".echo(); elseif (2==2) "2==2\n".echo(); else "none\n".echo();
2==2

switch

Grapa's switch statement is much more powerful than traditional switch statements. Each case can contain a full expression that returns true/false, and evaluation stops at the first match.

Basic switch without braces:

switch (x)
case 1: "One".echo();
case 2: "Two".echo();
default: "Other".echo();

With parentheses (optional):

switch (x)
case (1): "One".echo();
case (2): "Two".echo();
default: "Other".echo();

Complex expressions:

switch (data:{name: "Alice", scores: [85, 92, 78]})
case (data.scores.mean()[0] >= 90): "High performer".echo();
case (data.scores.mean()[0] >= 80): "Good performer".echo();
case (data.scores.min()[0] < 70): "Needs improvement".echo();
default: "Average performer".echo();

Multiple commands in case (use {}):

switch (x)
case 10: {
    "x is 10".echo();
    "Additional handling".echo();
}
case 5: {
    "x is 5".echo();
    "More handling".echo();
}
default: {
    "x is something else".echo();
    "Default handling".echo();
}

Boolean Expression Matching

/* Each case can be a full boolean expression */:
switch (true)
case (x < 0): "Negative".echo();
case (x == 0): "Zero".echo();
case (x > 0): "Positive".echo();
default: "Unknown".echo();

Complex Pattern Matching

/* Pattern matching on data structures */
user = {name: "Alice", age: 25, role: "admin"};

switch (true)
case (user.role == "admin" && user.age >= 18): "Admin access granted".echo();
case (user.role == "user" && user.age >= 18): "User access granted".echo();
case (user.age < 18): "Access denied - too young".echo();
default: "Access denied - unknown role".echo();

Variable Declaration in Switch Expression

Grapa's switch statement can declare and initialize variables directly in the switch expression, enabling advanced pattern matching and fuzzy matching:

/* Declare variable in switch expression for advanced matching */
switch(a:[1,3,5])
case (a[2]==5): "Array element matches".echo();
default: "No match found".echo();

Advanced Pattern Matching Examples:

/* Fuzzy string matching */
switch(input:"hello world")
case (input.grep("hello", "i")): "Contains 'hello' (case insensitive)".echo();:
case (input.len() > 10): "Long string".echo();
default: "No pattern match".echo();

/* Complex data structure analysis */
switch(data:{name: "Alice", scores: [85, 92, 78]})
case (data.scores.mean()[0] >= 90): "High performer".echo();
case (data.scores.mean()[0] >= 80): "Good performer".echo();
case (data.scores.min() < 70): "Needs improvement".echo();
default: "Average performer".echo();

/* Array pattern matching */
switch(arr:[1,2,3,4,5])
case (arr.len() == 5 && arr[0] == 1): "Five-element array starting with 1".echo();
case (arr.sum() > 10): "Array sum greater than 10".echo();
case (arr.grep(3)): "Array contains 3".echo();
default: "No specific pattern".echo();

Key Benefits: - Local scope: Variables are only available within the switch statement - Advanced matching: Enables fuzzy matching, pattern recognition, and complex conditions - Clean syntax: No need to declare variables before the switch - Temporary variables: Perfect for one-off calculations in switch logic

Type-Based Matching

/* Match based on data type */
switch (true)
case (data.type() == $STR): "String data".echo();
case (data.type() == $INT): "Integer data".echo();
case (data.type() == $LIST): "Array data".echo();
case (data.type() == $GOBJ): "List data".echo();
default: "Other data type".echo();

Exception Handling: try/catch/finally/throw

Grapa provides comprehensive exception handling with try/catch/finally blocks and throw statements.

Basic exception handling:

try throw 'error message'
catch 'error message': 'Caught specific error'.echo();
default: 'Caught any other error'.echo();
finally: 'Always executed'.echo();

With semicolon after try:

try throw 'error message';
catch 'error message': 'Caught specific error'.echo();
default: 'Caught any other error'.echo();
finally: 'Always executed'.echo();

Exception with variable binding:

try throw (err:'error message')
catch (err.left(1)=='e'): 'Error starts with e: '.interpolate({msg=err}).echo();
catch (err.len() > 10): 'Long error message'.echo();
default: 'Caught other error'.echo();
finally: 'Cleanup completed'.echo();

Multiple commands in catch (use {}):

try throw (err:'error message')
catch (err.left(1)=='e'): {
    'Error starts with e: '.interpolate({msg=err}).echo();
    'Additional error handling'.echo();
}
catch (err.len() > 10): 'Long error message'.echo();
default: 'Caught other error'.echo();
finally: 'Cleanup completed'.echo();

Object Variable Binding

/* Direct object throw - works correctly */
user = {name: 'Alice', age: 30};
try throw (err:user)
default: ('User name: ' + err.name).echo();

/* Nested object with explicit copy - works correctly */
user = {name: 'Alice', age: 30};
try throw (err:{user: user.gobj()})
default: ('User name: ' + err.user.name).echo();

/* Nested object without copy - works correctly */
user = {name: 'Alice', age: 30};
try throw (err:{user: user})  /* Local variable references are now preserved */
default: ('User name: ' + err.user.name).echo();

Note: Local variable references in thrown objects are now automatically preserved. The .gobj() method is no longer required for reliable binding.

Multiple Catch Blocks

/* Multiple catch blocks with different conditions */
try throw 'network error'
catch 'network error': 'Network issue handled'.echo();
catch 'file error': 'File issue handled'.echo();
catch (true): 'Any other error handled'.echo();
finally: 'Resource cleanup'.echo();

Exception Handling Syntax

Basic throw:

throw 'error message';
throw (err:'error message');  // With variable binding

Modern try/catch/finally syntax:

try throw 'error message'
catch 'error': 'Handle specific error'.echo();
catch (condition): 'Handle based on condition'.echo();
default: 'Handle any other error'.echo();
finally: 'Always execute'.echo();