Control Flow

Calor provides loops and conditionals with explicit structure.

Loops

For Loop Syntax

Plain Text

§L{id:var:from:to:step}
  // body

Part	Description
`id`	Unique loop identifier
`var`	Loop variable name
`from`	Starting value (inclusive)
`to`	Ending value (inclusive)
`step`	Increment per iteration

Examples

Count 1 to 10:

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§L{for1:i:1:10:1}
  §P i

Count down:

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§L{for1:i:10:1:-1}
  §P i

Count by 2s:

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§L{for1:i:0:100:2}
  §P i

Using variable bounds:

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§L{for1:i:1:n:1}
  §P i

Using expressions:

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§L{for1:i:0:(- n 1):1}
  §P i

While Loop Syntax

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§WH{id} condition
  // body

Part	Description
`id`	Unique loop identifier
`condition`	Boolean expression evaluated before each iteration

While Loop Examples

Simple countdown:

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§B{i} 10
§WH{while1} (> i 0)
  §P i
  §ASSIGN i (- i 1)

Read until done:

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§B{running} true
§WH{while1} running
  §B{input} §C{Console.ReadLine} §/C
  §IF{if1} (== input "quit")
    §ASSIGN running false

Do-While Loop Syntax

Plain Text

§DO{id}
  // body (executes at least once)

Part	Description
`id`	Unique loop identifier
`condition`	Boolean expression evaluated after each iteration

The condition is placed at the end to match the semantics: the body always executes at least once, then the condition is checked.

Do-While Loop Examples

Execute at least once:

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§B{i} 0
§DO{do1}
  §P i
  §ASSIGN i (+ i 1)

Menu loop (always show menu first):

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§B{choice} 0
§DO{do1}
  §P "1. Option A"
  §P "2. Option B"
  §P "3. Exit"
  §B{choice} §C{ReadChoice} §/C

Retry until success:

Plain Text

§B{success} false
§DO{do1}
  §B{success} §C{TryOperation} §/C

Dictionary Iteration

Use §EACHKV to iterate over key-value pairs in a dictionary.

Syntax

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§EACHKV{id:keyVar:valueVar} dictName
  // body uses keyVar and valueVar

Part	Description
`id`	Unique loop identifier
`keyVar`	Variable name for the current key
`valueVar`	Variable name for the current value
`dictName`	Name of the dictionary to iterate

Examples

Print all entries:

Plain Text

§DICT{ages:str:i32}
  §KV "alice" 30
  §KV "bob" 25

§EACHKV{e1:name:age} ages
  §P name
  §P age

Sum all values:

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§B{total} 0
§EACHKV{e1:k:v} scores
  §ASSIGN total (+ total v)

Conditional processing:

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§EACHKV{e1:key:val} data
  §IF{if1} (> val 100)
    §P key

Comparison with §FOREACH

Loop Type	Use Case
`§L{id:var:from:to:step}`	Numeric ranges
`§FOREACH{id:var} collection`	Lists, arrays, sets
`§EACHKV{id:k:v} dict`	Dictionaries (key-value pairs)

Conditionals

Single Line (Arrow Syntax)

For simple single-action branches:

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§IF{id} condition → action
§EI condition → action
§EL → action

Multi-Line (Block Syntax)

For complex branches:

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§IF{id} condition
  // multiple statements
§EI condition
  // multiple statements
§EL
  // multiple statements

Parts

Part	Description
`§IF cond`	If statement (block body indents below)
`condition`	Boolean expression
`→`	Arrow separator (single-line inline form)
`§EI`	Else-if (optional, can repeat) at same column as `§IF`
`§EL`	Else (optional, at most one) at same column as `§IF`
`§IF{id} cond`	Explicit ID form (optional, for tooling references)

Conditional Examples

Simple If

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§IF{if1} (> x 0) → §P "positive"

If-Else

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§IF{if1} (> x 0)
  §P "positive"
§EL
  §P "not positive"

If-ElseIf-Else

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§IF{if1} (> x 0)
  §P "positive"
§EI (< x 0)
  §P "negative"
§EL
  §P "zero"

Single Line with Multiple Branches

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§IF{if1} (== (% i 15) 0) → §P "FizzBuzz"
§EI (== (% i 3) 0) → §P "Fizz"
§EI (== (% i 5) 0) → §P "Buzz"
§EL → §P i

Nested Conditionals

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§IF{if1} (> x 0)
  §IF{if2} (< x 100)
    §P "between 0 and 100"
  §EL
    §P "100 or greater"

FizzBuzz Complete Example

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§M{m001:FizzBuzz}
  §F{f001:Main:pub}
    §O{void}
    §E{cw}
    §L{for1:i:1:100:1}
      §IF{if1} (== (% i 15) 0) → §P "FizzBuzz"
      §EI (== (% i 3) 0) → §P "Fizz"
      §EI (== (% i 5) 0) → §P "Buzz"
      §EL → §P i

Loop with Conditional

Plain Text

§M{m001:Example}
  §F{f001:PrintEvens:pub}
    §I{i32:n}
    §O{void}
    §E{cw}
    §Q (> n 0)
    §L{for1:i:1:n:1}
      §IF{if1} (== (% i 2) 0)
        §P i

Early Return

Use conditionals with return for early exit:

Plain Text

§F{f001:Factorial:pub}
  §I{i32:n}
  §O{i32}
  §Q (>= n 0)
  §IF{if1} (<= n 1) → §R 1
  §EL → §R (* n §C{Factorial} §A (- n 1) §/C)

Pattern Matching

Pattern matching provides concise multi-way branching with C# switch expression semantics.

Switch Expression Syntax

Plain Text

§W{id} expression
  §K pattern1 → result1
  §K pattern2 → result2
  §K _ → default

Part	Description
`§W expr`	Switch expression (cases indent below)
`expression`	Value to match against
`§K`	Case keyword (indented under `§W`)
`pattern`	Pattern to match
`→`	Arrow to result (single expression)
`_`	Wildcard (matches anything)
`§W{id} expr`	Explicit ID form (optional)

Literal Patterns

Match exact values:

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§B{day} §W{sw1} dayNum
  §K 0 → "Sunday"
  §K 1 → "Monday"
  §K 2 → "Tuesday"
  §K _ → "Other"

Relational Patterns (`§PREL`)

Match value ranges using relational operators:

Syntax	Meaning	C# Equivalent
`§PREL{gte} value`	Greater than or equal	`>= value`
`§PREL{gt} value`	Greater than	`> value`
`§PREL{lte} value`	Less than or equal	`<= value`
`§PREL{lt} value`	Less than	`< value`

Example - Grade calculation:

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§B{grade} §W{sw1} score
  §K §PREL{gte} 90 → "A"
  §K §PREL{gte} 80 → "B"
  §K §PREL{gte} 70 → "C"
  §K §PREL{gte} 60 → "D"
  §K _ → "F"

Variable Patterns with Guards (`§VAR`, `§WHEN`)

Capture the matched value and add conditions:

Plain Text

§B{desc} §W{sw1} value
  §K §VAR{n} §WHEN (> n 100) → "large positive"
  §K §VAR{n} §WHEN (> n 0) → "small positive"
  §K 0 → "zero"
  §K §VAR{n} §WHEN (> n -100) → "small negative"
  §K _ → "large negative"

Part	Description
`§VAR{name}`	Captures value into variable `name`
`§WHEN condition`	Guard condition (pattern matches only if true)

Option Patterns (`§SM`, `§NN`)

Match Option types:

Plain Text

§R §W{sw1} maybeValue
  §K §SM §VAR{v} → v        // Some(v) - extract value
  §K §NN → 0                 // None - default

Result Patterns (`§OK`, `§ERR`)

Match Result types:

Plain Text

§R §W{sw1} result
  §K §OK §VAR{v} → (+ "Success: " v)
  §K §ERR §VAR{e} → (+ "Error: " e)

Block Syntax (`§/K`)

For cases with multiple statements, use block syntax:

Plain Text

§W{sw1} x
  §K 1 → "one"              // Arrow syntax (single expression)
  §K 2
    §P "matched two"         // Block syntax (multiple statements)
    §R "two"
    §/K
  §K _ → "other"

Complete Example

Plain Text

§M{m001:HttpStatus}
  §F{f001:GetStatusMessage:pub}
    §I{i32:code}
    §O{str}
    §R §W{sw1} code
      §K 200 → "OK"
      §K 201 → "Created"
      §K 400 → "Bad Request"
      §K 404 → "Not Found"
      §K 500 → "Server Error"
      §K _ → "Unknown Status"

Why Explicit Loop IDs?

Precise targeting - "Modify loop for1" is unambiguous
Verification - Compiler uses indentation to determine loop boundaries
Agent-friendly - Easy to identify loop boundaries
Refactoring safe - IDs survive code movement

Why Arrow Syntax?

The arrow → provides:

Single-line clarity - §IF cond → action is compact
Readable flow - Condition "leads to" action
Consistent pattern - Same syntax for if, elseif, else

Contracts - Preconditions and postconditions