Programmer Guide/Command Reference/EVAL

Introduction

The EVAL command can be used to evaluate numerical expressions. These expressions may be built up from numerical constants, from scalar, vector, and matrix variables, and from a large number of functions and operators.

Syntax

An EVAL command uses the following general syntax:

result := eval expression

or

result := evalcheck expression

result

This is the target to be assigned with the result of the evaluation of the numerical expression. The result can be a shell variable, a Programmer_Guide/Shell_Items or a numerical object

expression

The numerical expression to be evaluated. The expression consists of numerical objects, functions and operators.

An expression may be either a numerical expression, e.g.

result := eval (5 * 10) % 3

or a subcommand, e.g.

result := eval init(10,1,1)

or a combination thereof:

result := eval 5+max(fill(6,1,1))

If the expression is syntactically ill-formed, an error (EVAL) or warning (EVALCHECK) is reported. See the example script expression_check.sts for details.

Numerical Objects

The following numerical objects are known to the EVAL command. The fields of the table item table are all numeric (you can use a parameter table). The value item value can contain numbers, vectors or matrices. The wave item wave is any wave item.

syntax	description	data type
constantNumber	a scalar constant. E.g. 4.5 or 4	scalar
table	the content of the whole table	vector, matrix
table[i,*] table[i,]	the i-th row of the table	scalar, vector
table[*,j] table[,j]	the j-th column of the table	scalar, vector
table[i,j]	the value of the i-th row and j-th column of the table	scalar
value	the content of the value item	scalar, vector, matrix
value[i,*] value[i,]	the i-th row of the value item	scalar, vector
value[*,j] value[,j]	the j-the column of the value item	scalar, vector
value[i,j]	the value of the i-th row and j-th column of the value item	scalar
wave[!signal,*] wave[!signal,]	the signal from all channels	vector, matrix
wave[!signal,ch]	the signal from channel ch (=1,2,...)	vector
wave[!signal,*,b,l]	the signal from all channels from sample b to sample b+l-1	vector, matrix
wave[!signal,ch,b,l]	the signal from channel ch from sample b to sample b+l-1	vector

Numerical Comparison Operators

The EVAL command supports the following numerical comparison operators:

>	less than
<	greater than
<=	less than or equal to
>=	greater than or equal to
==	equal to
!=	not equal to

Note that two numbers/vectors/matrices are considered equal if (and only if)

1. their dimensions are the same; and
2. all elements are numerically equal.

Logical Operators

The EVAL command supports the following logical operators:

||	logical or
&&	logical and
!	unary not

A C-like '? :' selection operator is also supported:

result := eval 1 < 2 ? 1+2 : 1-2 // result is 3

Note that unlike C, nested uses of this operator must be surrounded by brackets, e.g.:

result := eval 1 > 2 ? (5 == 5 ? 5 : 0) : (4 == 5 ? 3 : 4) // result is 4

EVAL subcommands

• abs
• absmax
• absmin
• absv
• acos
• aseg1
• asin
• asp2osp
• atan
• avr
• cepstrum
• complex arithmetic
• corr
• corrfun
• cos
• cvphase
• dct
• density
• dev
• dft
• dist
• em
• exp
• f0ac
• f0sp
• fft
• fill
• fir1
• floor
• formants
• grand
• haclust
• hcomb
• hist
• hth
• hz2bark
• hz2cent
• hz2erb
• hz2mel
• ifft
• iir1
• imax
• imin
• init
• int
• interp
• inv
• ipeak
• limit
• log
• log2lin
• lpc
• map2map
• mapmind
• max
• median
• min
• modclust
• mul
• ncol
• npow2
• nrow
• optmm
• otrack1
• pgget
• pghull
• pgiline
• pginit
• pgitest
• pgsplit
• pgtrans
• pgxgrid
• pztf
• qdet
• qinterp
• rand
• rleqs
• round
• rpoly
• rpolyreg
• sample
• select
• shuffle
• sig2osp
• sign
• sin
• sinc
• smooth
• sort
• sqrt
• sum
• svd
• tan
• ticks2f1
• trn
• var
• vmcol
• vmrow
• vsubc
• vsubn
• vv
• vvcat
• vvget
• vvset
• wconvert
• window
• wsum
• ydiff
• yint
• zcross

Examples

For an extensive list of examples, see the script eval_examples.sts: Programmer Guide/Command Reference/EVAL Examples/EVAL Examples

History

The EVAL command was added to the S_TOOLS-STx language in version 3.7.0. The EVAL command replaces and extends the EVALUATE command. If the EVAL command is not assigning to an existing item, a table is assigned. Note that the current maximum number of arguments is 64 (S_TOOLS-STx version 3.8.0). As of version 3.7.0, S_TOOLS-STx has more numerical objects than just the scalars INT and NUM.