# NMODL’s built-in functions

These functions, which are provided by the C language math library, can be called from within NMODL code. With the exception of **abs()**, all expect double-precision floating point arguments and return double-precision floating point values.

acos(x) - compute the arc cosine: Returns the arc cosine of its argument (arccos x). The argument must be in the range -1.0 to 1.0.

asin(x) - compute the arc sine: Returns the arc sine of its argument (arcsin x). The argument must be in the range -1.0 to 1.0.

atan(x) - compute the arc tangent: Returns the arc tangent of its argument (arctan x).

atan2(y,x) - compute the arc tangent of y/x: Returns the arc tangent of the ratio y/x (arctan y/x).

ceil(x) - round upwards: Returns the smallest integral value greater than or equal to its argument (x).

cos(x) - compute the cosine: Returns the cosine of its argument (cos x). The angle is expressed in radians.

cosh(x) - compute the hyperbolic cosine: Returns the hyperbolic cosine for a real argument (cosh x).

exp(x) - compute the exponential function: Returns the value of e raised to the argument power (\(e^x\)).

fabs(x) - compute the absolute value of a floating point number: Returns the absolute value of its argument (|x|).

floor(x) - round downwards: Returns the largest integral value less than or equal to its argument (x).

fmod(x,y) - compute x modulo y: Returns the value of x modulo y, the remainder resulting from x/y. (In Python this is

`x%y`

)

log(x) - compute the natural logarithm: Returns the natural logarithm of its argument (ln x).

log10(x) - compute the base 10 logarithm: Returns the base 10 logarithm of its argument (log10 x).

pow(x,y) - compute x raised to the y power: Returns the value of x raised to the power of y (\(x^y\)).

sin(x) - compute the sine: Returns the sine of its argument (sin x). The angle is expressed in radians.

sinh(x) - compute the hyperbolic sine: Returns the hyperbolic sine for a real argument (sinh x).

sqrt(x) - compute the square root: Returns the positive square root of its argument (\(\sqrt{x}\)).

tan(x) - compute the tangent: Returns the tangent of its argument (tan x). The angle is expressed in radians.

tanh(x) - compute the hyperbolic tangent: Returns the hyperbolic tangent for a real argument (tanh x).