Strings comparison

The string comparison operators are furmy two-letter commands. The one used most frequently is eq, for testing whether two strings are the same. Consider this new version of the hello.pl script. 

The various numeric and string comparison tests that were illustrated in the previous section evaluate to 1 when true and to the undefined value when false. 

This entire book is about the emergence, nature and cultivation of a new discipline, materials science and engineering. To draw together the strings of this story, it helps to be clear about what a scientific discipline actually is that, in turn, becomes clearer if one looks at the emergence of some earlier disciplines which have had more time to reach a condition of maturity. Comparisons can help in definition we can narrow a vague concept by examining what apparently diverse examples have in common. 

In this work the cases in the database are stored on their own MS-Excel worksheets. The stored cases are copied on a retrieval calculation data sheet during the retrieval phase. All retrieval parameters in this application are textual string parameters. Thus the comparison between casebase and input problem is simple. When the input value is equal with the case value, the distance is 1, otherwise the distance is 0. The weighted suitability of parameters is then calculated by Equation 9. The weighting factors are introduced by the user. Overall suitability is calculated by Equation 10. Cases are ranked according to their overall suitability and the five nearest cases are shown for the user on an output worksheet. 

Sequence comparison is a technique for comparing two strings, sequences, or vectors for the purpose of determining the distance between them, and consequently their relationship. The items making up the sequence could be numbers, symbols, tones, letters, or words. We could, for example, compute a metric distance between the names William and Victor. Recognizing this, it is a simple extension to understand that assertions concerning the causes of firm performance are sequences of words, and that sequence comparison methodology can be used to compute similarity measures between these assertions. 

Kruskal, J. B. 1987. Time Warps, String Edits, and Macromolecules The Theory and Practice of Sequence Comparison. Boston Addison-Wesley. 

The somewhat spherical shape of dendimers gives them some different properties in comparison to more linear macromolecules. On a macroscopic level, dendimers act as ball bearings rather than strings. In solution, viscosity increases as molecular weight increases for linear polymers. With dendrimers, viscosity also increases with molecular weight up to a point after which viscosity decreases as molecular weight continues to increase. 

A more sophisticated approach would be to tie the barometer to a string. Swing it as a pendulum. Calculate the value of g at the street and again at the top of the building. From the difference between the two values of g the height of the building, at least in principle, could be calculated. The student smiled and stated that he knew the conventional atmospheric pressure comparison answer, but that was neither the best practical answer nor the most accurate answer. 

D. Sankoff, and R. J. Cedergren, in Time Warps, String Edits and Macromolecules The Theory and Practice of Sequence Comparison (D. Sankoff and J. B. Kruskal, eds.), p. 253. Addison-Wesley, Reading, Massachusetts, 1983. 

Another important feature of InChl is its layered structure. Unlike in SMILES, where all data related to one atom are stored in one place, in InChl different properties of the structure are encoded in different parts of the identifier. This organization of the data has one very important advantage molecules with the same basic structure that differ only in some minor property, such as in stereochemistry or isotopic composition, have the same InChl, with only the exception of the corresponding layer. This makes it possible not only to compare two InChls to find if they represent exactly the same structure, but to use a more intelligent comparison of two InChl strings to reveal molecules with the same basic structure that differ only in some detail. It is then up to the user to decide which deviations in the InChl are significant for his or her purpose and which are not. 

Another set of early studies came from the work of Judson and coworkers [35, 36], which emphasized using GAs for search problems on small molecules and peptides, especially cyclic peptides. A dihedral angle representation was used for the peptides with values encoded as binary strings, and the energy function used the standard CHARMM force field. Mutations were implemented as bit flips and crossovers were introduced by a cut-and-paste of the strings. The small size of the system enabled a detailed investigation of the various parameters and policies chosen. In Ref. [37], a comparison between a GA and a direct search minimization was performed and showed the advantages and weaknesses of each method. As many concepts are shared between search problems on small peptides and complete proteins, these studies have contributed to subsequent attempts on full proteins. 

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