Chapter 19 Expressions

The syntax for expressions ($⟨$exp$\mathrm{⟩}$) is hierarchically defined below using infix operator expressions ($⟨$infix$\mathrm{⟩}$), function application expressions ($⟨$appexp$\mathrm{⟩}$), atomic expressions ($⟨$atexp$\mathrm{⟩}$).

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  expressions (top-level)
  

  $⟨$exp$\mathrm{⟩}$	::=	$⟨$infix$\mathrm{⟩}$
  	$|$	$⟨$exp$\mathrm{⟩}$ : $⟨$ty$\mathrm{⟩}$
  	$|$	$⟨$exp$\mathrm{⟩}$ andalso $⟨$exp$\mathrm{⟩}$
  	$|$	$⟨$exp$\mathrm{⟩}$ orelse $⟨$exp$\mathrm{⟩}$
  	$|$	$⟨$exp$\mathrm{⟩}$ handle $⟨$match$\mathrm{⟩}$
  	$|$	raise $⟨$exp$\mathrm{⟩}$
  	$|$	if $⟨$exp$\mathrm{⟩}$ then $⟨$exp$\mathrm{⟩}$ else $⟨$exp$\mathrm{⟩}$
  	$|$	while $⟨$exp$\mathrm{⟩}$ do $⟨$exp$\mathrm{⟩}$
  	$|$	case $⟨$exp$\mathrm{⟩}$ of $⟨$match$\mathrm{⟩}$
  	$|$	fn $⟨$match$\mathrm{⟩}$
  	$|$	_import $⟨$string$\mathrm{⟩}$ : $⟨$cfunty$\mathrm{⟩}$	importing C function
  	$|$	$⟨$exp$\mathrm{⟩}$ : _import $⟨$cfunty$\mathrm{⟩}$	importing C function
  	$|$	_sizeof( $⟨$ty$\mathrm{⟩}$ )	size of type
  	$|$	_dynamic $⟨$exp$\mathrm{⟩}$ as $⟨$ty$\mathrm{⟩}$	Dynamic type cast
  	$|$	_dynamiccase $⟨$exp$\mathrm{⟩}$ of $⟨$match$\mathrm{⟩}$	case branches with dynamic type cast
  	$|$	_sqlserver $($$⟨$appexp$\mathrm{⟩}$$\mathrm{)}\mathrm{?}$ : $⟨$ty$\mathrm{⟩}$	SQL servers
  	$|$	_sql $⟨$pat$\mathrm{⟩}$ => $⟨$sqlfn$\mathrm{⟩}$	SQL execution function
  	$|$	_sql $⟨$sql$\mathrm{⟩}$	SQL query fragments

  $⟨$match$\mathrm{⟩}$	::=	$⟨$pat$\mathrm{⟩}$ => $⟨$exp$\mathrm{⟩}$ $($| $⟨$match$\mathrm{⟩}$$\mathrm{)}\mathrm{?}$	pattern matching

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  infix operator expressions
  

  $⟨$infix$\mathrm{⟩}$	::=	$⟨$appexp$\mathrm{⟩}$
  	$|$	$⟨$infix$\mathrm{⟩}$ $⟨$vid$\mathrm{⟩}$ $⟨$infix$\mathrm{⟩}$

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  function application expressions
  

  $⟨$appexp$\mathrm{⟩}$	::=	$⟨$atexp$\mathrm{⟩}$
  	$|$	$⟨$appexp$\mathrm{⟩}$ $⟨$atexp$\mathrm{⟩}$	left associative function applications
  	$|$	$⟨$appexp$\mathrm{⟩}$ # { $⟨$exprow$\mathrm{⟩}$ }	record field updates

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  atomic expressions
  

  $⟨$atexp$\mathrm{⟩}$	::=	$⟨$scon$\mathrm{⟩}$	constants
  	$|$	$($op$)\mathrm{?}$ $⟨$longVid$\mathrm{⟩}$	identifiers
  	$|$	{$($$⟨$exprow$\mathrm{⟩}$$\mathrm{)}\mathrm{?}$ }	records
  	$|$	($\mathrm{⟨}$exp${}_{\mathrm{1}}$$\mathrm{⟩}$,$\mathrm{\cdots }$,$\mathrm{⟨}$exp${}_n$$\mathrm{⟩}$)	tuples ($n\ge 2$)
  	$|$	()	unit value
  	$|$	#$⟨$lab$\mathrm{⟩}$	record field selector
  	$|$	[$\mathrm{⟨}$exp${}_{\mathrm{1}}$$\mathrm{⟩}$,$\mathrm{\cdots }$,$\mathrm{⟨}$exp${}_n$$\mathrm{⟩}$]	lists ($n\ge 0$)
  	$|$	($\mathrm{⟨}$exp${}_{\mathrm{1}}$$\mathrm{⟩}$;$\mathrm{\cdots }$;$\mathrm{⟨}$exp${}_n$$\mathrm{⟩}$)	sequential execution
  	$|$	let $\mathrm{⟨}$declList$\mathrm{⟩}$ in $\mathrm{⟨}$exp${}_{\mathrm{1}}$$\mathrm{⟩}$;$\mathrm{\cdots }$;$\mathrm{⟨}$exp${}_n$$\mathrm{⟩}$ end	local declarations
  	$|$	_sql ($\mathrm{⟨}$sql$\mathrm{⟩}$)	SQL query fragments
  	$|$	($\mathrm{⟨}$exp$\mathrm{⟩}$)

  $⟨$exprow$\mathrm{⟩}$	::=	$⟨$lab$\mathrm{⟩}$ = $⟨$exp$\mathrm{⟩}$ $($, exprow$\mathrm{)}\mathrm{?}$	record fields

The definitions for $⟨$cfunty$\mathrm{⟩}$ is given in Section 19.21 and those for $⟨$sql$\mathrm{⟩}$ and $⟨$sqlfn$\mathrm{⟩}$ are given in Chapter 22.

The above hierarchical definition for expressions represents associatibity among expression constructors. The associatibity of infix operator expressions $⟨$infix$\mathrm{⟩}$ are determined not by syntax but by the infix operator declarations. In the following sections, we first define in the next (19.1) elaboration rules of infix expressions. In the following sections, we define each of expression constructors and their types in the order of associatibity.