ROOT - Interactive rootfinding

ROOT is a simple interactive program that allows you to set up a scalar nonlinear equation, an error tolerance, a function F(X), and some starting values, and then apply one of a number of methods for seeking a root of the equation F(X) = 0.

Files you may copy include:

• root.f90, the source code;

The list of routines includes:

• MAIN controls the interactive root finding program.
• BISECTION carries out the bisection algorithm.
• BRENT implements the Brent bisection-based zero finder.
• C_CAP capitalizes a single character.
• C_EQI is a case insensitive comparison of two characters for equality.
• C_IS_ALPHA returns TRUE if C is an alphabetic character.
• C_TO_DIGIT returns the integer value of a base 10 digit.
• COMRPN can translate formulas you type in and evaluate them.
• F is a function evaluation interface routine.
• FALSI carries out the Regula Falsi method.
• FIXED implements the fixed point method for a nonlinear equation.
• FUNSCL evaluates a scalar function of one or more scalar arguments.
• FUNVAL evaluates a scalar, vector or matrix valued function.
• HALLEY implements Halley's method for a nonlinear equation.
• HELP prints out a list of commands.
• I_GCF finds the greatest common factor of I and J.
• I_LCM computes the least common multiple of two integers.
• INICOM initializes data for COMRPN.
• INMETH allows the user to choose the method.
• LAGUERRE implements Laguerre's algorithm.
• MULLER carries out Muller's method.
• NEWTON carries out Newton's method.
• PCHECK performs some simple checks on the parentheses in a formula.
• PRLIST prints out the value of the algorithm parameters.
• R_SWAP switches two real values.
• RPNCHK examines IRPN, looking for a complete RPN expression.
• RPNSET converts the infix formula into an RPN formula.
• RPNVAL evaluates the symbolic functions in an RPN formula.
• S_BLANK_DELETE removes blanks from a string, left justifying the remainder.
• S_CAP replaces any lowercase letters by uppercase ones in a string.
• S_EQI is a case insensitive comparison of two strings for equality.
• S_IS_ALPHA returns .TRUE. if the string contains only alphabetic characters.
• S_TO_I reads an integer value from a string.
• S_TO_R reads a real number from a string.
• SECANT carries out the secant algorithm.
• SOLVE carries out the iteration procedure.
• STEFFENSON carries out Steffenson's method.
• SYMADD adds a symbol name to the list of symbolic names.
• SYMVAL sets, evaluates, or deletes a variable.
• TOKENS parses a character string into recognized symbols and constants.

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